Add an intermediate function to generate 2 paint-order lists.

Source/WebCore/rendering/RenderLayer.h

Index: Source/WebCore/rendering/RenderLayer.h
diff --git a/Source/WebCore/rendering/RenderLayer.h b/Source/WebCore/rendering/RenderLayer.h
index 21a6c919dc01fd742dd8ee8f5dc6b7e0f7ca60b8..75c08b342fa9371566fb470519e4fc8478c4bcfd 100644
--- a/Source/WebCore/rendering/RenderLayer.h
+++ b/Source/WebCore/rendering/RenderLayer.h
@@ -62,6 +62,7 @@ class FilterOperations;
 class HitTestRequest;
 class HitTestResult;
 class HitTestingTransformState;
+class PaintOrderLists;
 class RenderFlowThread;
 class RenderGeometryMap;
 class RenderLayerBacking;
@@ -834,12 +835,17 @@ public:
 
     bool isOutOfFlowRenderFlowThread() const { return renderer()->isOutOfFlowRenderFlowThread(); }
 
+    String paintOrderListsAsText();
+    PassRefPtr<PaintOrderLists> paintOrderLists();
+
 private:
     enum CollectLayersBehavior { StopAtStackingContexts, StopAtStackingContainers };
 
     void updateZOrderLists();
     void rebuildZOrderLists();
-    void rebuildZOrderLists(CollectLayersBehavior, OwnPtr<Vector<RenderLayer*> >&, OwnPtr<Vector<RenderLayer*> >&);
+    // See the comment for collectLayers for information about the
+    // layerToForceAsStackingContext parameter.
+    void rebuildZOrderLists(CollectLayersBehavior, OwnPtr<Vector<RenderLayer*> >&, OwnPtr<Vector<RenderLayer*> >&, const RenderLayer* layerToForceAsStackingContext = 0);
     void clearZOrderLists();
 
     void updateNormalFlowList();
@@ -854,6 +860,16 @@ private:
     bool acceleratedCompositingForOverflowScrollEnabled() const;
     void updateDescendantsAreContiguousInStackingOrder();
     void updateDescendantsAreContiguousInStackingOrderRecursive(const HashMap<const RenderLayer*, int>&, int& minIndex, int& maxIndex, int& count, bool firstIteration);
+    void collectBeforeAfterPromotionZOrderLists(RenderLayer* ancestorStackingContext,

[Ian Vollick, 2013/04/16 19:17:41]

Please combine these two methods. They're hard to distinguish by their names,
and looking at the .cpp, they could be merged. (And use the first, more
descriptive, method name).

[hartmanng, 2013/04/17 18:00:20]

Done.

+        OwnPtr<Vector<RenderLayer*> >& posZOrderListBeforePromote,
+        OwnPtr<Vector<RenderLayer*> >& negZOrderListBeforePromote,
+        OwnPtr<Vector<RenderLayer*> >& posZOrderListAfterPromote,
+        OwnPtr<Vector<RenderLayer*> >& negZOrderListAfterPromote);
+    void getPaintOrderLists(RenderLayer* ancestorStackingContext,
+        OwnPtr<Vector<RenderLayer*> >& posZOrderListBeforePromote,
+        OwnPtr<Vector<RenderLayer*> >& negZOrderListBeforePromote,
+        OwnPtr<Vector<RenderLayer*> >& posZOrderListAfterPromote,
+        OwnPtr<Vector<RenderLayer*> >& negZOrderListAfterPromote);
 
     void computeRepaintRects(const RenderLayerModelObject* repaintContainer, const RenderGeometryMap* = 0);
     void computeRepaintRectsIncludingDescendants();
@@ -908,7 +924,11 @@ private:
 
     LayoutPoint renderBoxLocation() const { return renderer()->isBox() ? toRenderBox(renderer())->location() : LayoutPoint(); }
 
-    void collectLayers(bool includeHiddenLayers, CollectLayersBehavior, OwnPtr<Vector<RenderLayer*> >&, OwnPtr<Vector<RenderLayer*> >&);
+    // layerToForceAsStackingContext allows us to build pre-promotion and
+    // post-promotion layer lists, by allowing us to treat a layer as if it is a
+    // stacking context, without adding a new member to RenderLayer or modifying
+    // the style (which could cause extra allocations).
+    void collectLayers(bool includeHiddenLayers, CollectLayersBehavior, OwnPtr<Vector<RenderLayer*> >&, OwnPtr<Vector<RenderLayer*> >&, const RenderLayer* layerToForceAsStackingContext = 0);
 
     void updateCompositingAndLayerListsIfNeeded();